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I never wrote down the grammar for the language, and I have also lost the Basic program. I did start writing a compiler for yet another (more elegant and powerful) language named Ecom using this language. The syntax of Ecom resembles that of the small language. This code did survive. What follows is based on analysing this code.
+ adding, +c adding with carry,
- subtracting, -c subtracting with carry,
& bitwise and, | bitwise inclusive or,
and : bitwise exclusive or.
All these operators have the same priority, and are executed from left
to right. Brackets can be used, if needed.
The following compare operators can be used to create conditional
expressions: <>, <=, <,
>, >=, and =.
Each conditonal expression should contain exactly one compare operator
Logical expressions are not available.
if, then,
elif, else, and fi.
The repeat-statement starts with the rep keyword, which
can be followed by any number of statements, and ends with a modified
form of the if-statement, which starts with the keyword rif.
In the clauses of this if-statement the keyword per can
be used to indicate that execution should continue at the start of
the repeat-statement.
write, and writel, a string can be printed,
where the writel will add a line break at the end.
Both these procedure can either have a constant string, or an array variable
as their argument.
The procedure readln, which should be called with an array
variable, reads a single line from the current channel.
The procedure use, which takes an integer constant, can be
used to select the current input/output channel.
The procedure aux, which takes an integer constant, can be
used to select the input/output mode.
The procedure open, which takes an string argument, can be
used to open a file, and the procedure close, which takes
an integer constant, can be used to close a channel.
The procedure dos, which has no arguments, can be used
to terminate the program and return to the Atari DOS prompt.
root : program eof .
program : ("var" (var_name ( "[" int "]" | "@" int )OPT )LIST ";" )OPT
("proc" proc_name ( "(" var_name ")" )OPT ";" program )CHAIN ";" OPT
"begin"
statements
"end".
statements : (statement CHAIN ";")OPT.
statement : var_name "[" expr "]" "=" expr
| var_name "=" expr
| "@" var_name "=" expr
| "if" cond_expr "then" statements "per" OPT
("elif" cond_expr "then" statements "per" OPT)SEQ OPT
("else" statements "per" OPT)OPT
"fi"
| "rep" statements
"rif" cond_expr "then" statements "per" OPT
("elif" cond_expr "then" statements "per" OPT)SEQ OPT
("else" statements "per" OPT)OPT
"fi"
| "return" expr
| proc_name ("(" expr ")")OPT
| "use" "(" int ")"
| "aux" "(" int ")"
| "open" "(" (var_name | string_const) ")"
| "close" "(" int ")"
| "write" "(" (var_name | string_const) ")"
| "writel" "(" (var_name | string_const) ")"
| "readln" "(" var_name ")"
| "dos"
.
cond_expr : exprr ("<>" | "<=" | "<" | ">=" | ">" | "=") expr
| expr .
expr : int
| char_const
| "(" expr ")"
| "@" var_name
| proc_name "(" expr ")"
| var_name ("[" expr "]")OPT
| expr ("+" | "+c" | "-" | "-c" | "&" | "|" | ":") expr
.
The terminals are defined as follows:
int : ("0" .. "9")SEQ.
char_const : "'" any_char "'".
string_cons : "'" non_single_quote_char "'".
var_name : ("a" .. "z")SEQ.
proc_name : ("a" .. "z")SEQ.
var a@218, as[80]These are used to store a line from the input. The variable
a
is placed in the zero-page.
top, depth, first[11],Used to manage the nested identifier scopes.
id[10],Contains the last identifier read from the input.
vn[100],ve[100],vt[100], vd[100],vv[100],vy[100], leng[100],type[100], adrl[100],adrh[100],Used to store information of up to hundered identifiers, with their storage length, type (e.g. procedure or variable name), and address.
pnr,padl[40],padh[40], sym, char[1], len,type,vnr, cl,ch,vl,vh, code[2],pcl,pch,(Unknown)
stack[100],sp,Contains the stack used during parsing.
ast,st, labk[3], labell[100],labelh[100],lnr, rlab, op, ofsetl,ofseth, startl,starth, file[16],flen;
proc err;
begin
use(0);writel('error');
char[0]=as[a];
write('at ');writel(char);
readln(as);
close(1);close(2);
dos
end;
proc typerr;
begin
use(0);writel('wrong type');err
end;
proc space;
begin
rep
rif as[a]=155
then use(1);
readln(as);
use(0);
writel(as);
use(2);
a=0 per
elif as[a]=' '
then a=a+1 per
fi
end;
proc symbol;
begin
space sym=scan(as)
end;
proc expect(s);
begin
if sym<>s
then use(0);char[0]=s;write(char);
writel(' expected');err
fi; symbol
end;
proc expch(ch);
begin
if as[a]<>ch
then use(0);char[0]=ch;write(char);
writel(' expected');err
fi; a=a+1; symbol
end;
proc testch(ch);
begin
if as[a]=ch then a=a+1; symbol; return 255
else return 0
fi
end;
proc ident;
var i,ch;
proc add;
begin
if i<6
then id[i]=ch; i=i+1
fi; a=a+1
end;
begin
space;
i=0;
rep ch=as[a]
rif ch>='a'
then if ch<='z' then add per fi
elif ch>='0'
then if ch<='9'
then if i<>0 then add per fi
fi
fi;
if i=0
then return 0
else rep rif i<6
then id[i]=' ';i=i+1 per
fi
fi
return 255
end;
proc lookup(eind);
var i;
begin
i=top;
rep i=i+1
rif i>=eind
then if id[0]=vn[i] then
if id[1]=ve[i] then
if id[2]=vt[i] then
if id[3]=vd[i] then
if id[4]=vv[i] then
if id[5]=vy[i]
then typ=type[i];
len=leng[i];
vnr=i;return i
fi fi fi fi fi fi
per
fi;
typ=0;
return 0;
end;
proc addvar;
begin
vn[top]=id[0];
ve[top]=id[1];
vt[top]=id[2];
vd[top]=id[3];
vv[top]=id[4];
vy[top]=id[5];
leng[top]=len;
type[top]=typ;
top=top+1;
if top>99
then use(0);
writel('too many vars');err
fi
end;
proc uniek
begin
if lookup(first[depth])<>0
then use(0);
writel('double def');
err
fi
end;
proc const;
var i;
proc readc(base);
var d;
proc add(v);
var lo,hi,i;
begin
lo=cl;hi=ch;i=1;
rep i=i+1;lo=lo+ cl;hi=hi+c ch
rip i<base then per
fi;
cl=lo+v;ch=hi+c0
end;
proc digit;
var ch;
begin
ch=as[a];
if ch<='9'
then if ch>='0'
then return ch-'0'
fi
elif ch<='f'
then if ch>='a'
then return ch-'a'+10
fi
fi;return 255
end;
begin
rep d=digit
rif d<base
then add(d);a=a+1;i=i+1 per
fi
end;
begin
i=0;ch=0;cl=0;
if testch(''')<>0
then i=1;cl=as[a];a=a+1; expch(''')
elif testch('#')<>0 then readc(16)
elif testch('b')<>0 then readc(2)
else readch(10)
fi; symbol; return i;
end
proc c(cod)
begin
@code=cod;
code[0]=code[0]+1;code[1]=code[1]+c0;
pcl=pcl+1;pch=pch+c0
end;
proc push(i)
begin
stack[sp]=i;
sp=sp+1;
if sp=100
then use(0);writel('stckover');err
fi
end;
proc pop;
begin
if sp=0
then use(0);writel('stckunder');err
fi
sp=sp-1;
return stack[sp]
end;
proc adrvnr;
begin
vl=adrl(vnr);
vh=adrh(vnr)
end;
proc pla;
begin
if ast=1 then c(104) fi
end;
proc pha;
begin
if ast=1 then c(72) fi
end;
proc pusha;
begin
push(ast);pha;ast=0
end;
proc incvnr;
begin
vl=vl+1;vh=vh+c0
end;
proc acode;
begin
c(vl);c(vh)
end;
proc icode(i);
begin
if i=0 then c(208)
elif i=1 then c(144);c(5);c(240)
elif i=2 then c(144);
elif i=3 then c(176);
elif i=4 then c(144);c(2);c(268)
elif i=5 then c(240)
fi; c(3)
end;
proc lcode;
begin
if st>12
then c(8);c(169);c(255);c(40);
icode(st-25);c(169);c(0);c(234);
st=1
fi
end;
proc mcode(base);
begin
lcode;
if st<=3
then if st=1 then c(133)
elif st=2 then c(135)
else c(132)
fi; c(212);
if st=1 then c(104) fi;
c(base-4);c(212)
elif st=4 then c(base);c(cl)
elif st=5 then c(base+4);acode
elif st=6 then c(base+20);acode
elif st=7 then c(base+16);acode
elif if vh<>0
then pha;c(173);c(vl);c(vh);
c(133);c(213);incvnr;
c(173);c(vl);ch(vh);
c(133);c(214);vl=213;pla
fi;
if st=8 then c(base-8)
else c(base+8)
fi; c(vl)
fi; st=1
end;
proc sta;
begin
if st=1 then
elif st=2 then c(170)
elif st=3 then c(168)
elif st>=5
then if st<=9
then mcode(137)
else typerr
fi
else typerr
fi
end;
prov lda;
begin
lcode;
if st<>1
then pha; ast=1;
if st=2 then c(138)
elif st=3 then c(152)
else mcode(169)
fi; st=1
fi
end;
proc ocode;
begin
if op=17 then sta
elif op=18 then mcode(105)
elif op=19 then c(24);mcode(105)
elif op=20 then mcode(233)
elif op=21 then c(56);mcode(233)
elif op=22 then mcode(41)
elif op=23 then mcode(9)
elif op=24 then mcode(73)
else mcode(201);st=op
fi
end;
proc jmpto(lab);
begin
c(242);c(76);c(lab)
end;
proc makelab(lab);
begin
labell[lab]=pcl;labelh[lab]=pch
end;
proc newlab;
begin
if lnr=99
then use(0);writel('tm lab');err
fi;
lnr=lnr+1
end;
proc jmptol(l);
begin
if labk[l]=0
then labk[l]=newlab
fi;
jmpto(labk(l))
end;
proc makecl(l);
begin
if labk[l]<>0
then makelabel(labk[l])
fi
end;
proc monad(s);
begin
if st=2
then if s=1 then c(232)
elif s=2 then c(202)
else typerr
fi
elif st=3
then if s=1 then c(200)
elif s=2 then c(184)
else typerr
fi
else if s=1 then s=238
elif s=2 then s=206
elif s=3 then s=14
elif s=4 then s=46
elif s=5 then s=78
elif s=6 then s=110
else typerr;
if st=5 then c(s);acode
elif st=6 then c(s+16);acode
else typerr
fi
fi
end;
list : expr CHAIN ";".is parsed by:
proc list;
begin
if sym>=8
then if sym<=14 then st=1;return 0
fi
fi;
rep ast=0;st=0;expr
rif testch(';')<>0 then per
fi;
if ast=0 then lda fi
end
do_expr : "do" list "od".is parsed by:
proc doexpr;
begin
rlab=rlab+1;labell[rlab]=pcl;labelh[rlab]=pch;
push(labk[0]);labk[0]=0;
pusha;list;ast=pop;st=1;
if sym=12
then symbol;c(76);c(labell[rlab]);
c(labelh[rlab])
fi; expect(14);
makecl(0);labk[0]=pop;rlab=rlab-1
end
if_expr : "if" expr "then" list
("elif" expr "then" list)SEQ OPT
("else" list)OPT
"fi"
is parsed by:
proc ifexpr;
var nlab;
proc endthen;
begin
if sym=12
then if rlab=0 then err fi;
symbol;c(76);c(labell[rlab]);
c(labelh[rlab])
elif sym=13
then if rlab=0 then err fi;
symbol;jmptol(0)
elif sym<>11
then jmptol(1)
fi
end;
begin
push(labk[1]);labk(1)=0;
push(labk[1]);push(nlab);pusha;
rep
nlab=newlab;labk[2]=0;
rep symbol;ast=0;st=0;expr;
if st<12 then lda;st=25 fi
rif sym=16
then icode(30-st);jmptol(2) per
else icode(st-25);jmpto(nlab);
if sym=15 then per
fi; expect(6);makecl(2);
list;endthen;makelab(nlab)
fi;
rif sym=9 then per
elif sym=10 then symbol;list;endthen
fi;
expect(11);
makel(1);ast=pop;st=1;
nlab=pop;labk[2]=pop;labk[1]=pop
end;
array ("." const)OPT
("[" expr "]")OPT.
is parsed by:
proc array;
bein
if typ=2
then adrvnr;st=5
elif if typ<>3 then typerr fi;
if testch('.')<>0
then const else cl=0
fi;
if testch('[')<>0
then push(cl);
push(ast);push(vnr);
expr;lcode;vnr=pop;
if st=1 then c(168)
elif st<=3 then st=st+4
elif st=4 then c( );c(cl);st=7;
elif st=5 then c( );c(vl);c(vh);st=7
else pha;mcode(169);c(168);
st=1
fi;
ast=pop;
if st=1 then st=7;pla fi;
cl=pop;expch(']')
else st=5
fi;
vl=adrl(vnr)+ cl;vh=adrh(vnr)+c0
fi
end;
proc expid;
begin
if ident=0
then use(0);writel('no id');err
elif lookup(1)=0
then use(0);writel('undef');err
fi; symbol
end;
factor : "(" expr ")"
| "a"
| "x"
| "y"
| do_expr
| if_expr
| "begin" list "end"
| "?" ident array
| const
| ident ( array | "(" var ")" )OPT
.
is parsed by:
proc factor;
begin
if testch('(')<>0
then expr;expch(')')
elif testch('a')<>0 then st=1
elif testch('x')<>0 then st=2
elif testch('y')<>0 then st=3
elif sym=7 then symbol;doexpr
elif sym=5 then ifexpr
elif sym=4 then symbol;pusha;list;ast=pop;expect(8)
elif testch('?')<>0
then expid;array;
if st=5 then c(160);c(0);st=9
elif st=6 then st=8
elif st=7 then st=9
fi
elif sym<>0
then use(0);writel('ilsym');err
elif const<>0 then st=4
else expid;
if typ>=2
then array
else pusha;
if len>0
then expch('(');push(vnr);
expr;lda;var;pop;
expch(')')
fi;
if type[vnr]=0
then c(242);c(32);c(adrh[vnr])
else c(32);c(adrl[vnr]);c(adrh[vnr])
fi;
st=1;ast=pop
fi
fi
end;
oper : "->"
| "+c" | "+" | "-" | "-c"
| "&" | "|" | ":"
| "<>" | "<=" | "<"
| ">=" | ">" | "="
| "inc" | "dec"
| "ror" | "rol" | "lsr" | "asl"
.
is parsed by:
proc oper;
begin
if sym>=17
then if sym<36
then op=sym;symbol;return 1
fi
fi; return 0
end;
expr : factor CHAIN oper.is parsed by:
proc expr;
begin
factor;
if oper<>0
then lda;
rep
if st>12 then lcode fi;
if op>=33
then const;
if op=33 then op=
elif op=34 then op=
elif op=35 then op=
else op=
fi;
cl=cl&7;
rep c(op);cl=cl-1
rif cl>0 then per
fi
else push(op);factor;op=pop;
opcode
fi
rif oper<>0 then per
fi
fi
end;
vars : "var"
( ident ( "[" const "]"
| "?" | "$" )OPT
( "@" const )OPT
) CHAIN "," ";" .
is parsed by:
proc vars;
begin
symbol;
rep
ident; uniek; space;
if testch('[')<gt;0
then const; len=cl;typ=3;
space;expch(']')
else testch('?')
then len=2;typ=3
elif testch('$')
then len=3;typ=3
else len=1;typ=1
fi;
if testch('@')<gt;0
then const;space
else cl=ofsetl;ch=ofseth;
ofsetl=cl+len;ofseth+c0
fi;
adrl[top]=cl;adrh[top]=ch;
addvar;
rif testch(',')<gt;0
then per
fi; expch(';')
end;
procs : ident ( "(" ident ")" )OPT ":"
vars OPT
procs SEQ OPT
factor ";"
.
is parsed by:
proc procs;
var par
begin
symbol;ident;
if lookup(first[depth])=0
then typ=1;var=top;
if as[a]='(' then len=1 else len=0 fi;
addvar
else if typ<>0 then err fi;
len=leng[vnr]
fi; push(vnr);
depth=depth+1;
if depth>10
then use(0);writel('too deep');err
fi; first[depth]=top;
if len=1
then expch('(');ident;push(vnr)
adrl[top]=ofsetl;adrh[top]=ofseth;
ofsetl=ofsetl+1;ofseth=ofseth+c0;addvar;expch(')')
else push(0)
fi; expch(':');
if sym=1 then vars fi;
rep rif sym=3 then procs per fi;
par=pop;vnr=pop;typ=type[vnr];
if typ=0
then symbol;pnr=pnr+1;
adrl[vnr]=pnr;typ=0
fi;
if typ=1
then adrl[vnr]=pcl;adrl[vnr]=pch;
if par<>0
then c(141);c(adrl[par]);c(adrh[par])
fi; factor; c(96)
fi;expch(';');
top=first[depth];
depth=depth-1
end;
program : vars OPT
procs SEQ OPT
"begin" list "end".
is parsed the first time by:
proc passone;
begin
first[0]=1;depth=0;top=1;
sp=0;pnr=0;
lnr=0;rlab=0;
file[flen]=84;file[flen+1]=88;
file[flen+2]=84;
use(0);write('reading: ');writel(file);
use(1);aux(4);open(file);
a=0;as[0]=155;
symbol;
if sym=1 then vars fi;
rep rif sym=3 then procs per fi;
startl=pcl;starth=pch;
expect(4);list;c(96);
if sym<gt;8 then err fi;
use(0);
writel('program o.k.');
close(1)
end;
The second pass, patches the code, such that the
right addresses are filled in:
proc passtwo;
var endl,endh;
proc w(op);
begin
char[0]=0;write(char);
end;
proc n;
var res;
begin
res=@code;
code[0]=code[0]+1;code[1]=code[1]+c0;
return res
end;
proc trans(op);
begin
if op&8=0
then if op=32 then w(op); w(n); w(n)
elif op&159=0 then w(op);
elif op&15<>2 then w(op);w(n)
elif op=242
then op=n;w(op);
if op=32
then op=n;w(padl[op]);w(padh[op])
else op=n;w(labell[op]);w(padh[op])
fi
fi
elif op&13=8 then w(op)
elif op&31=9 then w(op);w(n)
else w(op);w(n);w(n)
fi
end;
begin
endl=code[0];endh=code[1];code[0]=...;code[1]=...
rep
trans(n)
rif code[1]<endh then per
elif code[0]<endl then per
fi; w..
end;
The main body of the program is missing.